Track-type machines typically include a track assembly having a plurality of interlocking links, each link being coupled to a ground-engaging traction panel. Adjacent links may be interconnected via a laterally disposed track pin to form a continuous chain. A rotatable bushing may be disposed about the track pin, the rotatable bushing being configured to rotate relative to the track pin. The rotatable bushing is adapted to engage a portion of a sprocketed drive hub. As a drive motor rotates the sprocketed drive hub, teeth of the sprocketed drive hub engage spaces between the bushings forcing the track link to move in the direction of rotation of the hub, thereby propelling the machine.
Because the rotatable bushing enables rotation of the track bushing relative to the track link, which decreases the friction at the interface between the bushing and the sprocket, track assemblies that employ the rotatable bushings may be less susceptible to wear caused by friction than track assemblies with stationary (i.e., non-rotatable) bushings. However, because the friction for track links having rotatable bushings is significantly lower than track links with stationary bushings, rotatable bushings may be more susceptible to accidental rolling or slipping out of the space defined by the teeth of the sprocket. Under heavy loading conditions, this slippage can cause the track to seemingly “jump” during operation of the machine, potentially leading to premature wear (or breakage) of the teeth of the drive sprocket. This phenomenon may also negatively impact the operator's ability to control the machine.
To reduce bushing slippage and track “jumping” caused by such slippage, some systems rely on increasing the width and size of the components that interact with the drive sprocket, thereby increasing the surface area of the component at the sprocket interface, which effectively increases the friction force—a force which must be overcome in order to for the bushing to slip or jump. For example, U.S. Pat. No. 7,201,242 (“the '242 patent”) to Tucker, Jr. discloses a tracked-belt driven vehicle having a drive sprocket with spaces that interact with rubber drive lugs of a drive belt. In order to reduce the tendency of the rubber drive lugs to deform under heavy loading conditions (which can lead to slipping), the vehicle of the '242 patent employs drive lugs with larger-than-conventional width and height parameters that are designed to more precisely conform to the size and shape of the drive sprocket. Increasing the size of the drive lugs may increase the surface area of interaction between the drive sprocket and the drive lugs, potentially reducing the deforming effects of “point loading” on the lugs. By increasing the surface area of interaction, the prior art system may also effectively increase the friction force, reducing the likelihood of track slipping and/or jumping.
Although increasing the width and size of the drive sprocket and the drive lugs to increase the surface area of interaction therebetween may reduce deformation of the drive lugs and “jumping” of the drive belt in certain situations, it may have significant disadvantages. For example, increasing the amount of material on the track assembly may increase manufacturing and material costs of the machine. Furthermore, increasing the width and size of the drive sprocket and drive lugs may unnecessarily add to the weight of the track assembly, effectively decreasing the power to weight ratio (efficiency) of the machine.
The presently disclosed sprocketed drive assembly for a track-type machine is directed to overcoming one or more of the problems set forth above.